1. Field of the Invention
This invention relates to new fluorine-containing polyamide-polyamide-polyimide polymers and polybenzoxazole-polyamide-polyimide polymers derived therefrom which exhibit improved thermal stability, improved resistance to solvents, good processability, good film-forming properties and good film characteristics.
2. Description of Related Art
Polyimides derived from aromatic diamine and dianhydride monomers are widely used in the aerospace industry and electronics industry because of their toughness, low density, thermal stability, radiation resistance, mechanical strength and good dielectric properties. However, such polyimides are often difficult to process thermally and thin films prepared therefrom are often brittle and lack acceptable optical transparency.
It has been suggested that aromatic polyimides having the hexafluoroisopropylidene linking group in the diamine and/or dianhydride monomer have improved solubility and processing properties. For example, U.S. Pat. No. 3,356,648 to Rogers discloses polyimides prepared from 2,2-bis(4-aminophenyl) hexafluoropropane; U.S. Pat. No. 4,592,925 to DuPont discloses polyimides prepared from 2,2-bis(3-aminophenyl) hexafluoropropane; U.S. Pat. No. 4,111,906 to Jones et al. discloses polyimides prepared from 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane; and U.S. Pat. No. 4,477,648 to Jones et al. discloses polyimides prepared from 2,2-bis[(2-halo-4-amino-phenoxy)phenyl] hexafluoropropane. U.S. Pat. No. 4,592,925 discloses polyimides prepared by reacting 2,2-bis(3-aminophenyl) hexafluoropropane and 4,4'-hexafluoroisopropylidene-bis (phthalic anhydride), also known as 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride.
In addition, U.S. Pat. No. 3,179,635 discloses the preparation of polyamide-polyimide polymers said to have good thermal stability and good film-forming properties which may be prepared by condensing a tetra functional aromatic dianhydride, an aromatic diamine and an aromatic acid halide. Polyamides and polybenzoxazole derivatives thereof based on the condensation product of aromatic diamines and aromatic dicarboxylic acids and their derivatives are disclosed in U.S. Pat. Nos. 3,306,876, 3,449,296 and 4,622,285. U.K. patent application No. GB-2188936A discloses the preparation of polyamides and polybenzoxazole derivatives thereof based on the condensation product of 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane with an aromatic dicarboxylic acid or acid halide, followed by cyclization of the polyamide to form a polybenzoxazole. Similar fluorine-containing polyamides are disclosed in U.S. Pat. No. 3,328,352.
In applicant's co-pending application Ser. No. 076,098, filed in the U.S. Patent and Trademark Office on July 21, 1987, is disclosed hydroxy polyimide polymers which, in the preferred embodiment, are prepared by forming the polymeric condensation product of hexafluoro-2,2-bis(3-amino-4-hydroxyphenyl) propane and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride. These polymers are particularly useful in the preparation of photoresist compositions.
Polyamide-imide polymers and copolymers are also known in the art. These materials are generally prepared by the condensation polymerization of trifunctional acid monomers such as the 4-acid chloride of trimellitic anhydride and one or more aromatic diamines. Examples of such polyamide-imide polymers are disclosed in U.S. Pat. Nos. 3,347,828, 3,494,890, 3,661,832 and 3,920,612. These polymers may be characterized by extremely good high temperature properties (Tg of about 275.degree. C. or higher), good high temperature stability, good tensile strength at high temperatures, good mechanical properties and good chemical resistance. These polyamide-imides are useful as wire enamel coatings, laminates, molded products, films, fibers impregnating varnishes and in other applications where high thermal stability is required.
One of the problems associated with such polyamide-imide polymers is that they exhibit generally poor flow properties which render them difficult to process, particularly to injection mold or to spin into fibers. These polymers are also relatively hydrophilic and tend to absorb moisture which can effect their clarity, heat stability, processability and electrical properties.
Attempts have been made in the art to improve the flow properties of polyamide-imide polymers. For example, U.S. Pat. No. 4,448,925 discloses including from about 1 to about 10 percent phthalic anhydride into the polymerization recipe to provide polyamide-imide copolymers having improved flow properties. However, this technique for improving flow properties is made at the expense of the heat stability and chemical resistance of the polymer. Yet another method for improving the flow properties of such polymers is to form blends thereof with up to about 10% by weight of a polyamide such as nylon 6 or nylon 66, as disclosed in U.S. Pat. No. 4,575,924. Once again however, such an approach to solving the flow problem is made at the expense of the thermal stability and optical clarity of the resultant polymer blend.
Whereas the above-referred to polyimides, polyamide-polyimide and polybenzoxazole polymers are useful for the utilities disclosed, it is desirable to provide polyamide-polyimide polymers and polybenzoxazole polymers which provide not only superior thermal and thermooxidative stability, but also excellent thermal processability, low moisture uptake, low dielectric constant and good film-forming properties and film characteristics.